High-density optical data storage unit and method for writing and reading information

ABSTRACT

This high-density optical data storage unit comprises a storage medium supported on a mechanically stable substrate, and a read/write arrangement employing a plurality of laser light sources and an interrogation light source. The laser light sources are designed as laser diodes attached to a substrate and optically aligned with an equal plurality of microlenses integrated in a first transparent layer. The read/write arrangement further comprises at least one second transparent layer, and an optional semitransparent conductive coating, said layer or said coating carrying a plurality of particulate protrusions which are also aligned with said diodes and said microlenses, said storage medium and said read/write arrangement being maintained in a mutually parallel alignment with a gap in between having a width of less than 100 nm. The protrusions in combination with the laser light sources produce dints in the medium which are representative of the data to be stored. The data is read by using the interrogation light source to produce light which is scattered by the dints and is then detected by the diodes.

This application is a continuation of application Ser. No. 08/311,823,filed on Sep. 22, 1994, now U.S. Pat. No. 5,461,600, which is acontinuation of U.S. application Ser. No. 07/978,015, filed on Nov. 18,1992, now abandoned, entitled "HIGH-DENSITY OPTICAL DATA STORAGE UNITAND METHOD FOR WRITING AND READING INFORMATION", in the name of WolfgangD. Pohl.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a high-density optical storage unit forstoring and retrieving electronic information, including encoded data,text, image, and audio information, and a method for writing and readingthe information. "High-density" in this context shall mean densities ofstored bits of information in excess of 10⁹ bit/cm².

2. Description of the Prior Art

In conventional optical storage units, the shape and the size of thestored bits are defined by the narrow focal point of a laser beam,making the circular bit regions about 1 micrometer in diameter. Thismeans that the storage density is limited to about 10¹⁰ bits/cm². Thewell-known (read-only) compact disk (CD) can store approximately 10¹⁰bits of information on its entire active surface, for example.

Regarding the storage media used in conventional erasable (read/write)storage units, there are essentially two groups of leading opticalcontenders each requiring its own technique for reading and writinginformation: Magneto-optic and phase-change materials. Both techniquesemploy glass or plastic disks coated with thin films of storagematerial; they depend on lasers for recording, yet their approach towriting and reading information is markedly different.

As is well known (e.g., from J. C. Iwata, "Optical Storage," IBMResearch Magazine, Vol. 25, No. 1, pp. 4-7, 1987), magneto-opticrecording relies on heating, by a laser beam, and in the presence of anexternal magnetic field, a thin film of magnetic material coated onto asubstrate. As the temperature of the film is locally raised above theCurie point of the material, the external magnetic field will reversethe original direction of the magnetization at the particular location,and as the spot involved cools, the new direction of the magnetizationis "frozen," thus storing a bit of information.

The stored information is read by flashing a laser beam, though atreduced power, onto the storage medium causing those storage locationsholding magnetization with a changed direction to slightly rotate theplane of polarization of the reflected beam, a phenomenon known as theKerr effect. This rotation can be sensed by a photodetector and thestored bit identified.

Erasure of the stored information is done by simply heating theparticular storage area to a temperature above the Curie point in thepresence of a magnetic field having the original direction.

In phase-change recording, a short (less than 100 ns) burst of laserlight converts a tiny spot on the media's highly reflective crystallinesurface to the less reflective amorphous, or semicrystalline state, theconversion occurring upon rapidly heating the material to a temperatureabove its melting point, then rapidly quenching it, "freezing" it intothe amorphous state.

For reading the stored information, a laser beam is scanned over theamorphous and crystalline storage locations; the variations of thereflected light are detected and the locations storing a bit ofinformation identified.

Restoring the storage medium to its original state is done by heatingthe bit locations to a temperature below the material's melting point,but for an "extended" period of time (on the order of 10-⁵ S).

Both these techniques have the severe disadvantage of being limited inminiaturization by diffraction to a bit size of about λ/2.

Under the present invention, several recording schemes are conceivable,and two such schemes and the appertaining storage media will bediscussed below by way of example. The first scheme to be discussedoperates with a thermoplastically deformable storage material in whichthe bits of information are stored in the form of tiny dints produced byheat and pressure. The second scheme is an electro-optical system usinga storage material which has the capability of trapping electricalcharges when illuminated by light having a sufficiently shortwavelength.

The feature common to these schemes is the accessing in two discretesteps: In a first step, light selects an area of a few squaremicrometers as determined by the diffraction limit, and in a secondstep, a small protrusion selects a bit of much smaller size, say assmall as a fraction of 0.01 μm square, within said area. In this manner,a very large number of tips, potentially millions, can be operated inparallel.

Work on surface modification by means of a laser-heated tip pressed intoa thermoplastically deformable material was reported by H. J. Mamin andD. Rugar in their abstract "Laser-Assisted Nanolithography with an AFM,"Bull. Am. Phys. Soc., Vol. 37 (1992) p. 565/6, paper No. M28 5.

Writing information into storage by means of charge injection with asingle tip and silicon nitride as the storage medium is known from R. C.Barrett and C. F. Quate, "Charge storage in a nitride-oxide-siliconmedium by scanning capacitance microscopy," J. Appl. Phys. 70 (5), Sep.1, 1991, pp. 2725-2733.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the disadvantagesof the prior references and/or to further develop the techniques showntherein, and to advance the art of information storage towards higherbit densities, i.e. to higher storage capacities.

The present invention achieves this object by providing a high-densityoptical data storage unit capable of performing a two-step process ofaddressing, and comprising a storage medium having a plurality ofstorage cells which each comprise a plurality of bit areas, said storagemedium being supported on a mechanically stable substrate, and aread/write arrangement employing a plurality of read/write lightsources/detectors and an interrogation light source. The optical datastorage unit of the invention is characterized in that said read/writearrangement comprises a first portion composed of diffraction-limitedoptical elements for addressing any selected one of said plurality ofstorage cells, and a second portion composed of near-field opticalelements for selecting any one of said plurality of bit areas within therespective addressed storage cell.

The first portion composed of diffraction-limited optical elementscomprises a plurality of semiconductor diodes that can be operated bothas light sources and light detectors, and which are geometricallyaligned with an equal plurality of microlenses embedded in a transparentlayer, and the second portion composed of near-field optical elementscomprises a plurality of particulate protrusions which are alsogeometrically aligned with said diodes and with said microlenses, saidstorage medium and said read/write arrangement being maintained in amutually parallel alignment with a gap in between having a width of lessthan 100 nm.

The object is also achieved by the inventive method for writing/readinginformation into/out of the data storage unit described above, which ischaracterized by the following two-step addressing scheme: (1) Selectionof the bit cells in an array of bit cells by activation of one or moreof said laser light sources and their associated optical elements, and(2) selection of individual single-bit areas by means of optical fieldconcentration at the location of said particulate protrusions. Thismethod involves the following steps for writing information: mutuallyparallel displacing the surfaces of said read/write arrangement and ofsaid storage medium in order to align a selected one of said particulateprotrusions with a selected bit location within the associated bit cell,locally changing the characteristics of said storage medium so as tostore a bit of information therein.

Under this invention, the following steps are performed for readinginformation from an arbitrary number of cells in parallel: Mutuallyparallel displacing the surfaces of said read/write arrangement and ofsaid storage medium in order to align a selected one of said particulateprotrusions with the bit location within the associated bit cell fromwhich information is to be read, activating said interrogation lightsource to cause a light wave to enter into the storage unit, said lightwave being particularly scattered at said protrusions and illuminatingthe diodes associated with those storage locations whose characteristicswere previously changed, said diodes then generating an electric outputsignal representative of the information read.

Details of two embodiments of the invention as well as of the inventivemethod for data storage and retrieval will hereafter be described by wayof example, with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a partial cross section of a first embodiment of thestorage unit in accordance with the invention;

FIG. 2 shows the cross-section of FIG. 1 during the writing process,with three bits being stored;

FIG. 3 shows a partial cross section of a second embodiment of thestorage unit in accordance with the invention;

FIG. 4 shows a schematic diagram of a mechanism designed to maintainflats 1 and 2 at all times in a truly parallel relationship.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As mentioned above, the storage density in conventional optical storageunits is naturally limited by the smallest diameter to which a laserbeam can be focused, and that is >300 nm. Thus, with a bit diameter of 1μm, a storage density of about 10⁸ bit/cm² results. The concept of thepresent invention in contrast employs some of the techniques developedin connection with the scanning near-field optical microscope whichpermit a considerably smaller bit size, namely on the order of 10-100 nmand, hence, a storage density of better than 10¹⁰ bit/cm², as will beexplained below.

FIG. 1 shows a partial cross section of a first embodiment of thestorage unit in accordance with the invention, the storage unitessentially comprising two flats 1 and 2, respectively acting as recordcarrier (1) and probe head (2), a light source 3, and control and driveelectronics 4 which permit to mutually displace the facing surfaces offlats 1 and 2, and to maintain them in a parallel alignment with a gapwidth of between 5 and 15 nm even during the displacement. It is knownto those skilled in the art that piezoceramic actuators allow fordisplacements in the 10-100 μm range. Such actuators can be usedadvantageously in connection with the invention.

In view of the small gap size between flats 1 and 2, their facingsurfaces must be machined to a planarity of 3-5 nm over an area of 3-10mm diameter, corresponding to a finish of "λ/100" with respect tooptical wavelengths. Also, the said surfaces are to be kept parallelwithin the same tolerance of 3-5 nm. It should be noted that thesetolerances are standard in high-quality optical interferometry.Preferably, the gap size is controlled by a two-stage mechanism, onestage providing for a rough approach between flats 1 and 2, the otherstage permitting fine adjustment of the distance under feedback control.The techniques required to do this may be borrowed from scanning probemicroscopies (`SXM`) and from interferometric techniques.

In the first embodiment being described, flat 1, the record carrier,essentially comprises a mechanically stable substrate 5 and, on top ofit, a storage medium in the form of a thin layer 6 of a suitablematerial which plastically deforms when placed under pressure and heatedlocally, with a laser beam, for example. Such a record carrier obviouslypermits a multitude of information bits to be stored over a principallyunlimited period of time.

Flat 2, the probe head, comprises a mechanically stable substrate 7carrying an array of light-emitting diodes 8 (which may be laserdiodes), optionally an opaque screen 9 having holes 10 transparent tothe light emitted by the diodes 8 and centered with respect to saiddiodes 8. Flat 2 further comprises a transparent spacer layer 11integrating an array of microlenses 12 having a focal length in the10-100 μm range, a transparent layer 13 of low-refractive index materialserving as a spacer and as a substrate for a thin high-refractive indexlayer 14 acting as the core of an optical waveguide system formed bysaid layers 13 and 14, the upper pan of the gap 15 between flats 1 and2, and by a very thin semitransparent coating 16, which may be metallic(gold and silver are favored) or nonmetallic (e.g. tin oxide SnO₂).Coating 16 bears an array of small particles 17 of equal size and shape,with a diameter in the range between 10 and 100 nm. Their shape may be(semi-)ellipsoidal with an excentricity between 0 (half-spheres) andabout 10 (needles). They may also have the shape of short cylinders, ofcones, or of pyramids.

Regarding the fabrication of the array of diodes 8 (assuming a 100×100array occupying about 3 by 3 mm), standard techniques may be employed.Also, the various layers of different materials, namely layers 9, 11,13, 14, and 16, as well as lenses 12 and protrusions 17 can be producedby standard deposition techniques.

The particles 17 sitting on coating 16 may be metallic or non-metallic.They may, for example, be produced by conventional lithography in that asuitable mask with holes is placed on top of coating 16, and the metalis deposited (by evaporation or sputtering) through those holes, forminglittle pyramids or needles similar to those used in scanning forcemicroscopy with micromechanical probes.

One method for depositing material with nanometer dimensions isdescribed in EP-A-0 166 119 where free metal atoms supplied to a sharplypointed tip by sputtering or evaporation are field-desorbed anddeposited on a surface under the influence of a strong electric fieldexisting between the tip and said surface.

In accordance with the teaching of EP-A-0 196 346, the particles 17 mayalso be generated by photo-dissociation of a metalliferous gas under theinfluence of a laser beam focused in an optical waveguide, which resultsin the bonding of free metal atoms on the surface of coating 16.

Still another method for producing the particles 17 can be taken from apaper by H. J. Mamin et al., "Atomic Emission from a Gold Scanning-Tunneling-Microscope Tip," Phys. Rev. Lett. 65, No. 19 (1990) pp.2418-2421, where free metal atoms are deposited by means of fieldevaporation from the tip of a scanning tunneling microscope.

As mentioned before, the particles 17 should have the same size. If thefabrication process does not provide the desired uniformity, correctionscan be made by field evaporation from the too far protruding particles.

As an alternative, the particles 17 may be composed of polystyrenespherules having equal diameters in the range between 25 and 90 nm.These spherules are adsorbed at the surface of coating 16, and both,coating 16 and the spherules are then covered with a gold film which mayhave a thickness of up to 20 nm. (cf. U. Ch. Fischer and D. W. Pohl,"Observation of Single-Particle Plasmons by Near-Field OpticalMicroscopy," Phys. Rev. Lett. 62, No. 4 (1989) pp. 458-461).

Again referring to FIG. 1, light source 3 (which is used to interrogatethe state of the individual storage locations) consists of a laseroperating at a wavelength for which the laser diodes 8 arephoto-sensitive and can be used as light detectors. The laser beam fromsource 3 is fed into the waveguide structure formed by layers 13 to 16,and gap 15 between flats 1 and 2. To avoid scattering at the array ofmicrolenses 12, the low-refractive index layer 13 is chosen sufficientlythick. After passage through the waveguide, the laser beam can either besent into an absorber or sent back into the laser. Standard couplers,such as prisms or gratings can be used to feed the laser beam into andout from the waveguide.

In operation, flats 1 and 2 are approached to each other so that the gapbetween the surface of storage medium 6 and the particles 17 is ≦10 nm.The addressing of the individual storage locations is performed inparallel by laterally displacing the flats 1 and 2 by a distance suchthat the desired storage locations are placed opposite the particles 17.When illuminated, the latter represent perturbations of the light pathgiving rise to field concentration and light scattering in alldirections.

For writing, flat 2 is lowered onto flat 1 so far that the particles 17exert a small force onto storage medium layer 6. The force is adjustedto a value safely below the elasticity value of the storage medium. Thisadjustment can, for example, be made with the use of techniques borrowedfrom scanning force microscopy, as will be obvious to those skilled inthe art. Then those laser diodes (8a, 8d, and 8e) which are associatedwith the areas selected to store a "1" bit at the given address areenergized.

The energized laser diodes 8a, 8d and 8e each generate a laser beamproviding enough heat--optionally through enhancement by plasmonexcitation--to warm up the associated particles 17a, 17d and 17e tocause the storage medium layer 6 to deform plastically beneath them andform an array of dints 18a 18d and 18e. When the laser diodes 8a, 8d and8e are turned off and flat 2 is retracted, layer 6 will quickly cooldown to a temperature well below the melting point thereof, and thuspermit the dints to become "frozen" and, hence, the respectiveinformation bits to remain stored. The dints may have a depth of 20-50nm, provided the arrangement is properly adjusted.

The speed of writing information into the storage medium 6 is mainlylimited by the speed of the mechanical motion with which flat 2 can berepositioned between two consecutive storage operations, i.e. from onestorage location to the next. Assuming 10 μs per repositioning cycle andan array of 33×33 bit positions, the writing speed will be about 10⁸bit/s.

For reading, interrogation light source 3 is turned on. The lightentering the waveguide composed of the layers 13 to 16 and the upperpart of gap 15 between flats 1 and 2, is scattered at all imperfectionsencountered, in particular at the particles 17. It is known from theearlier-mentioned Fischer-Pohl reference in Phys. Rev. Lett. 62 (1989)pp. 458-461, that the intensity of scattering depends on the distance ofthe medium next to the particles 17. At the sites of the dints 18a, 18dand 18e the distance is larger by about 20 to 50 nm, and this results ina strong variation of the scattering intensity at these locations, thefactor of increase or decrease, depending on adjustment, shape andmaterials parameters, being 2-3, under favorable conditions up to 10.

Such a factor of increase of the scattering intensity is sufficient forthe laser diodes 8 to distinguish between the "normal" scatteringoccurring at all particles 17 and that occurring at the locations of thedints, i.e. at the stored "1" bits. The reading process can be very fastsince diodes have rise times on the order of nanoseconds.

The erasure of the stored bits would require the leveling of the dints18 generated in storage medium 6. In view of the fact that in thegeneration of the dints heat was used, one might consider heating theentire storage medium to a temperature where the viscosity of thestorage material is decreased so as to cause it to flow sufficiently toreestablish a smooth surface.

As mentioned above, the mutual displacement of flats 1 and 2 can beperformed by piezoceramic actuators under control of control and driveelectronics 4. The actuators can be activated so that each one of theparticles 17 sequentially addresses all storage locations within an areadetermined by the maximum elongation/contraction of the piezoceramicactuators used. This area is defined as one bit cell.

On the assumption that the particles 17 have diameters in the rangebetween 10 and 100 nm, one can conservatively calculate with a bitsizeof about 100 nm (diameter). With a scan range of 30 μm defining astorage cell, one obtains a storage capacity of ≈10⁵ bit/cell. With anarray size of 100×100 cells--corresponding to a total storage area of3×3 mm--the entire storage capacity becomes ≈1 Gbit, corresponding to astorage density of better than 10¹⁰ bit/cm².

In the case of digital recording of data, the control and driveelectronics 4 may, for example, be controlled in such a way that foreach "1" bit of information a dint 18 is produced, whereas the "0" bitdoes not produce any change in the storage medium, but there is noreason why the association cannot be the other way around.

In the case of analog recording of information, such as voice or music,the control and drive electronics 4 can be controlled in such a way, forexample, that the depth of the dints created in the storage medium 6depends on the dynamics of the information to be stored. Thus, a "forte"portion of the information would result in a deeper dint, for example,than a "piano" portion.

The second storage scheme in accordance with the invention which willhereafter be discussed, is an electro-optical system using a storagematerial which has the capability of trapping electrical charges andchanging its refractive index because of the resulting fields. Anexample of such a material is potassium tantalum niobate (KTN). Thestorage medium could also be composed of two individual layers of whichone is optimized for charge storage (e.g. Si₃ N₄), the other forelectro-optic activity.

As FIG. 3 shows, the structure of this second embodiment is essentiallythe same as that of the first embodiment (therefore, all identical partsretain their original reference numbers in FIG. 3), with the exceptionof the storage medium, as follows: Substram 19 Of flat 1 consists of amechanically stable, electrically conductive material. It carries aphotoconductive layer 20 with a particularly high dark-resistance.Deposited on photoconductive layer 20 is a layer 21 of anelectro-optically active material, such as the before-mentionedpotassium tantalum niobate. Layer 21 should be thin enough to allow foreffective injection, by field-emission, of charges from the particles 17of flat 2, or from substrate 19 while photoconductive layer 20 is in itslow-resistance state.

The addressing of the individual storage locations is performed the sameway as explained in connection with the first-described embodiment ofthe invention: A particular bit is accessed by enabling the diode 8which is associated with the storage cell to which the bit locationbelongs, while the corresponding particle 17 is positioned above the bitbeing addressed.

For writing, a voltage sufficient for charge injection intoelectro-optically active layer 21 is applied between coating 16 and,hence, particles 17 and substrate 19. A light pulse from the addresseddiode 8 renders the path between the respective particle 17 andsubstrate 19 through layer 20 sufficiently conductive for chargeinjection to occur in the area underneath said particle 17. This isaccomplished by the static field concentration at particle 17 on the onehand, and by the concentration of the optical near-field withcorrespondingly increased photoconductivity of layer 20 on the otherhand.

In FIG. 3, diodes 8a and 8d may be considered to be activated andexciting surface plasmons at their associated particles 17a and 17d (cf.the above-cited Fischer-Pohl reference). Associated with the plasmons isa particularly strong electric field enhancement with factors >10 foroptimal conditions. These strong fields act to locally change thecharacteristics of the electro-optically active layer 21 at positions22a and 22d facing said excited particles 17a and 17d.

The reading operation is performed the same as explained in connectionwith the first-described embodiment of the invention: Laser light source3 is energized, and the laser light is fed into the waveguide formed bylayer 14 and coating 16 of flat 2, the gap 15 between flats 1 and 2, andelectro-optically active layer 21 of flat 1. The light wave getsscattered at all particles 17 extending into gap 15. Since the intensityof scattering depends on the properties of the environment of theparticles 17, it varies with the alteration of the refractive indexwhere any particular particle 17 is paired with a charge stored in thefacing position of electro-optically active layer 21. The variationagain may be enhanced by the excitation of surface plasmons at particles17a and 17d. The scattered light is collected by the associated lenses12a and 12d of the array of microlenses 12 and focused onto the diodes8a and 8d, respectively.

To erase the entire information stored, a very strong light wave isentered into the waveguide 13-16, 21. The light wave will destroy thecharges stored so that the storage medium 21 is ready again for afurther storage cycle. Alternatively, the charges stored may be removedthrough the application of an electric field of suitable directionbetween coating 16 and photoconductor layer 20 while the latter isilluminated for resistance reduction thereof.

Erasure of individual stored bits is accomplished by operating theassociated diodes as light emitters while the control and driveelectronics 4 cause mutual displacement of flats 1 and 2.

Cycle time, bitsize and storage capacity achievable with this secondembodiment of the invention essentially correspond to those obtainedwith the embodiment described first.

Very important is the exact parallel positioning of the working surfacesof flats 1 and 2 with respect to one another. One option is theapplication of interferometric techniques exploiting the fact that thesurfaces of the two flats 1 and 2 are arranged as in a Fabry-Perotinterferometer. Active mirror adjustment devices that operate with thedegree of precision required here are commercially available.

Another option for parallel positioning will now be described withreference to FIG. 4 which shows a simple means to maintain flats 1 and 2at all times in a truly parallel relationship, i.e. within a toleranceof 3 to 5 nm, even during lateral displacement. Maintained suspended ina rigid frame 23 is flat 2 by means of control and drive electronics 4.The lower surface of flat 2, represented by coating 16 with itsparticles 17 faces the upper surface of the storage medium 6; 20, 21 offlat 1, to which it is supposed to be parallel. Flat 1 rests on anadjustment block 24 which is supported within frame 23 by piezoelectricactuators 25 and 26. Rigidly attached to at least two sides of flat 1are tunneling transducers 27 and 28 comprising tunnel tips 29 and 30which cooperate with lateral extensions 31, 32 of particle-carryingcoating 16.

In operation, assuming proper tunneling regimes and proper parallelismof the surfaces of coating 16 and storage medium 6, 21, equal andconstant tunneling currents will flow across the gaps between tunneltips 29, 30 and extensions 31, 32, respectively. Any deviation fromparallelism will cause a drastic alteration of at least one of thetunneling currents. In a feedback loop (not shown) a correction signalwill be sent back to either one or both of actuators 25, 26, causingappropriate tilting of adjustment block 24 and, hence, flat 1, toreestablish the parallel alignment of flats 1 and 2.

It will be obvious to those skilled in the art that the same adjustmenteffect can be achieved without lateral extensions 31, 32, by havingtunnel tips 29, 30 cooperate directly with the lower surface of layer16, provided the latter is conducting. Alternatively, if layer 16 isnon-conducting, it will be possible to provide a force microscopearrangement where tips 29, 30 are supported on very thin cantilevers,and the deviation of the cantilevers under the influence of atomic (Vander Waals, etc.) forces is monitored to control the adjustment ofparallelism.

While the preferred embodiments of the present invention have beenillustrated in detail, it should be apparent that modifications andadaptations to those embodiments may occur to one skilled in the artwithout departing from the scope of the present invention as set forthin the following claims.

What is claimed is:
 1. An optical data storage system comprising:a datastorage medium having a plurality of data bit areas; a plurality of nearfield optical elements each having a diameter in the range of 10-100nanometers, each located proximate one of the data bit areas; aninterrogation light source for providing light to the near field opticalelements; and a plurality of diffraction limited optical elements, eachassociated with one of the near field optical elements, each opticalelement for receiving particularly scattered light from its associatednear field optical element.
 2. The system of claim 1, wherein the nearfield optical elements are protrusions from a planar surface, the datastorage medium is comprised of a deformable material, and wherein theoptical data storage system further comprises a movement means formoving the near field optical elements into contact with the datastorage medium, and means for individually providing a light beam toeach near field optical element.
 3. The system of claim 1, wherein thediffraction limited optical elements comprise a plurality of diodeswhich are capable of operating both as a light source and a lightdetector.
 4. The system of claim 1, further comprising a plurality ofmicrolenses, each associated with one of the plurality of near fieldoptical elements, the microlenses for providing optical communicationbetween each near field optical element and its associated diffractionlimited optical element.
 5. The system of claim 1, further comprising anoptical waveguide located between the plurality of near field opticalelements and the plurality of diffraction limited optical elements, theoptical waveguide receiving light from the interrogation light sourceand distributing it to the plurality of near field optical elements. 6.The system of claim 1, wherein selected data bit areas of the datastorage medium have indentations.
 7. The system of claim 1, wherein thedata storage medium is comprised of a thermoplastic material.
 8. Thesystem of claim 1, wherein the distance between the near field opticalelements and the data storage medium is less than 100 nanometers.
 9. Thesystem of claim 1, further comprising movement means connected to theplurality of near field optical elements for moving the near fieldoptical elements in a direction lateral to a surface of the data storagemedium.
 10. The system of claim 1, further comprising movement means formoving the near field optical elements in a direction perpendicular to asurface of the data storage medium.
 11. The system of claim 10, whereinthe movement means comprises a piezoelectric actuator.
 12. The system ofclaim 10, further comprising an adjustment device for controlling themovement means in order to maintain the proper distance between the nearfield optical elements and the surface of the data storage medium. 13.The system of claim 12, wherein the adjustment device comprises atunneling transducer.
 14. A method for reading data from a data storagesystem comprising a data storage medium having a plurality of data bitareas, a probe head having a plurality of near field optical elementseach optical element having a diameter in the range of 10-100nanometers, each located proximate one of the data bit areas, aninterrogation light source for providing light to the near field opticalelements, and a plurality of diffraction limited optical elements, eachassociated with one of the near field optical elements, each diffractionlimited optical element for receiving particularly scattered light fromits associated near field optical element, the process comprising thefollowing steps:positioning the near field optical elements proximate asurface of the data storage medium; providing a beam of light from theinterrogation light source to the near field optical elements such thatthe light beam is particularly scattered at the near field opticalelements; and receiving light from each near field optical element at anassociated diffraction limited optical element.
 15. The system of claim14, further comprising the step of laterally displacing the probe headrelative to the medium.
 16. A method for recording data in a datastorage system comprising a data storage medium having a plurality ofdata bit areas, a probe head having a plurality of near field opticalelements having a diameter in the range of 10-100 nanometers, eachlocated proximate one of the data bit areas, a plurality of lightemitting diodes, each associated with one of the near field opticalelements, the process comprising the following steps:moving the probehead such that the near field optical elements exert pressure on thestorage medium; energizing selected diodes associated with selected nearfield optical elements so as to heat said selected near field opticalelements to a temperature at which the material of said data storagemedium starts flowing and an indentation is formed in the data storagemedium; deenergizing said selected diodes and moving the probe head awayfrom the data storage medium, thereby removing the impact of said nearfield optical elements from said data storage medium and permitting thedata storage medium to cool, thus preserving the indentations.
 17. Themethod of claim 16, further comprising the step of laterally displacingthe probe head relative to the medium.
 18. A data storage medium havingindentations formed using the method of claim 16.